The induction of glutamine synthetase in HTC cells as well as in human fibroblasts and in 3T3 cells will be examined further. The requirements for induction, the dose response curve for both L-glutamine (which prevents induction of the enzyme) and glucocorticoids, the time course, and the rate of decline of high activity levels in induced cells to base line when the cells are washed and returned to glutamine containing medium without glucocorticoids will be studied in detail. Covalent modification of the enzyme will be sought as one mechanism to account for the rapid fall of enzymatic activity previously described. Attempts also will be made to identity a peptide containing the modified cysteinyl residues at or near the active site of glutamine synthetase from Bacillus subtilis. These studies will be done collaboratively with Dr. Robert Heinrikson of the University of Chicago. AMP deaminase will be further characterized using techniques of amino acid analysis, ultracentrifugation, and gel filtration. The binding of the enzyme to the inner surface of the erythrocyte membrane will be established with the highly purified preparations available. The association constant and number of binding sites on the erythrocyte membrane surface of AMP deaminase will be determined also.